The invention relates to a radial piston pump having an eccentric actuator unit with several pump pistons driven by a common drive shaft.
A number of radial piston pumps are known, by means in which a delivery volume can be adjusted by means of an eccentric. The disadvantage of these is that the eccentric surfaces run parallel with a drive shaft and the delivery volume can therefore only be adjusted by displacing the central axis of the eccentric relative to the central axis of the drive shaft. The delivery volume is often adjusted purely on the basis of pressure. Radial piston pumps of this type are very complex to manufacture because a separate drive has to be provided for the pressure medium, to which external pressure is applied.
The objective of the invention is to provide a pumping system of the type having a radial piston pump with an eccentric actuator unit, which will allow largely automatic regulation of the delivery volume depending on the system pressure during operation.
This object is accomplished by the invention with a radial piston pump comprising a plate-shaped housing having bores for conveying a fluid medium, a drive unit joined to the housing at one side thereof and having a drive shaft projecting through the housing, a storage container for the fluid medium fluid-tightly joined to the housing at a side thereof opposite to the one side, and pumping units comprising pump pistons arranged at the opposite side of the plate-shaped housing, the pump pistons circumferentially surrounding the drive shaft and being radially displaceable relative thereto. An eccentric actuator unit radially displaces the pump pistons, the actuator unit having an axially extending bore receiving the drive shaft, being axially displaceably mounted on the drive shaft and keyed thereto for rotation therewith, and the actuator unit to the axis of the drive shaft and a like inclined surface bearing on the pump pistons.
The surprising advantage of this system is that in order to regulate the pumping rate of a pump equipped with any number of pumping units to cope with the demands of prevailing requiroments, a mechanically simple and hence reliable control system is provided between the drive unit and the pumping system, designed to permit automatic regulation so that predetermined work rates can be obtained irrespective of the consumers used, and the strokes of the pump pistons and hence their delivery rate may be varied.
A reproducible initial position will remain unchanged for a predetermined, structurally created eccentricity if a biasing mechanism is provided for displacing the actuator unit into an end position against a stop axially spaced from the housing, the biasing mechanism comprising return springs arranged in, and substantially parallel to, the axially extending actuator unit bore.
A bearing design which is capable of absorbing the spring forces with virtually no wear is provided with an annular bearing seat supporting the return springs at ends thereof opposite the stop. The bearing seat is a ring surrounding a cylindrical portion of the actuator unit axially projecting from the cylindrical body having an inclined axis, further comprising a radial bearing supporting the bearing ring and bearing the cylindrical portion of the actuator unit.
If a spring couples the actuator unit to the drive shaft for locking the actuator unit against rotation relative to the drive shaft, the rotary motion of the drive shaft is transmitted via the biasing spring to the actuator unit free of backlash, without restricting the capacity of the actuator unit to move axially on the drive shaft.
Advantageously, the radial piston pump further comprises a casing circumferentially surrounding an end of the actuator unit remote from the drive unit, and an actuator arranged in the casing. A thrust bearing is arranged between a pressure plate of the actuator and an end face of a recess of the actuator unit. A biasing mechanism displaces the actuator unit into an end position against the pressure plate of the actuator, and the actuator comprises a pressure medium activated plunger exerting an axial bias force opposite the bias force exerted by the biasing mechanism. The plunger is connected to the pressure plate by a press-fit to prevent displacement.
As a result of these, the delivery volume can be controlled externally in order to adjust the pumping rate to an adjustment curve predetermined on the basis of specific operating conditions and the mechanism used for this purpose can be obtained using simple and reliable transmission components known from the prior art.
If the pumping units have outlets communicating with each other by bores in the plate-shaped housing, the bores constituting pressure lines for the fluid medium, assembly is simplified since loss of load due to the pipework is reduced to a minimum and faults caused by leakage which might otherwise occur due to the stress of vibration on screw fittings and pipework are avoided.
A compact structure is provided if a flanged bearing plate affixes the plate-shaped housing and a pump housing for the pump pistons arranged at the opposite side thereof to the drive unit.
Advantageously, the pistons carry piston shoes in contact with the inclined bearing surface of the cylindrical body of the actuator unit. The piston shoes are able to move on all sides enabling them to adapt to every possible angle.